Apparatus for and method of adjustably precalibrating the position of the focal spot of an X-ray tube for use in a CT scanner system
The invention provides a system for and method of precalibrating the position of the focal spot of an X-ray tube before its installation in a CT scanner system so that the focal spot of the tube is properly aligned with the off-focal aperture, slice-defining aperture and detectors of the scanner system. The precalibration is performed using an interface registration support that receives the X-ray tube and supports the X-ray tube on a mount provided in either the precalibration system or the scanner system. The mount of the precalibration system duplicates the mount of the scanner system, so that desired position of the focal spot in the scanner system relative to the scanner system mount is duplicated in the precalibration system relative to the precalibration system mount. Adjustments in the position of the focal spot are carried out by measuring any displacement of the focal spot of the X-ray tube relative to an interface registration support which is referenced to the desired position of the focal spot by registering the registration support to the mount of the precalibration system. The as-adjusted X-ray tube and its interface registration support can then be installed in the CT scanner without the need for subsequent calibration adjustments. Additional testing of the X-ray tube can also be provided.
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Claims
1. An apparatus for precalibrating the position of the focal spot of an energy source adapted for use in an energy system prior to mounting the energy source in the energy system so that said focal spot will be correctly positioned within the system when the energy source is mounted in the system, said apparatus comprising:
- detector means for receiving and detecting energy emitted by said energy source;
- means for defining at least three beam paths which intersect at a predetermined point in space which is the desired spatial position of said focal spot when said energy source is mounted in said energy system;
- support means for supporting said energy source; and
- adjustment means, coupled to said support means, for controllably adjusting the position of said energy source relative to said support means prior to mounting the energy source in the energy system until the detection of energy by said detector means satisfies an alignment condition.
2. The apparatus as recited in claim 1, wherein said energy source is an X-ray tube intended for use in a CT scanner system including a detector array, and said detector means includes at least one detector for detecting the displacement of said focal spot in the Z-axis direction as defined by said scanner system, and said adjustment means moves said tube so that the alignment condition is effective in aligning said energy source with said detector.
3. The apparatus as recited in claim 1, wherein the alignment condition is defined by a geometrical relationship between said focal spot and said detector means that represents a desired alignment of said focal spot with respect to a scan detector array in a computer tomographic (CT) scanner system that is produced if said energy source, as supported by said support means and adjusted by said adjustment means, is integrated with said CT scanner system according to a predetermined mounting scheme.
4. The apparatus as recited in claim 1, further comprising:
- analysis means for analyzing the energy detected by said detector means and for determining when said alignment condition is reached.
5. The apparatus as recited in claim 1, wherein said means for defining at least three beam paths comprises a system of apertures associated with said energy source.
6. The apparatus as recited in claim 1, further including means for testing the operational parameters of said energy source.
7. The apparatus as recited in claim 6, wherein the means for testing the operational parameters of said energy source includes means for testing the focal spot position drift with temperature.
8. The apparatus as recited in claim 6, wherein the means for testing the operational parameters of said energy source includes means for measuring the focal spot size in two dimensions.
9. The apparatus as recited in claim 6, wherein the energy source is an X-ray tube, and the means for testing the operational parameters of said energy source include means for measuring the X-ray intensity noise from said tube.
10. The apparatus as recited in claim 6, wherein the means for testing the operational parameters of said energy source includes means for measuring the wobble and drift of the focal spot.
11. The apparatus as recited in claim 6, wherein said energy source is an X-ray tube, said apparatus further includes a power supply for powering said energy source, and wherein the means for testing the operational parameters of said energy source includes means for measuring the intensity of the X-rays emitted by said tube, for a given voltage and current provided by the power supply.
12. The apparatus as recited in claim 6, wherein said energy source is an X-ray tube, said apparatus further includes a power supply for powering said energy source, and wherein the means for testing the operational parameters of said energy source includes means for measuring fluctuations of X-ray intensity of the X-rays emitted by said tube not due to motion of said focal spot.
13. The apparatus as recited in claim 6, wherein the energy source is an X-ray source for use in a fan beam CT scanner system, said X-ray tube includes at least a tube aperture for defining a fan beam angle, and the means for testing the operational parameters of said energy source includes means for measuring the fan beam angle provided from said X-ray source.
14. The apparatus as recited in claim 13, wherein said means for measuring the fan beam angle includes fan beam detector means for detecting the edges of said fan beam.
15. The apparatus as recited in claim 14, wherein said fan beam detector means includes a pair of detectors.
16. The apparatus as recited in claim 1, wherein the energy system comprises (a) system mount means for supporting said support means in a precise position, and (b) at least one other system component positioned so as to be precisely spaced from the desired position of said energy source and said system mount means, said apparatus further comprising:
- apparatus mount means for supporting said support means and substantially identical to said system mount means to the extent that when the position of said energy source relative to said support means is at the desired position where the detection of energy by said detector means satisfies the alignment condition, the energy source and said support means can be supported by said system mount means and be correctly positioned in said energy system relative to said system component.
17. The apparatus as recited in claim 16, wherein the support means comprises:
- source flange means for securing said energy source to said support means;
- mount flange means for securing said support means to either one of said apparatus mount means and system mount means;
- adjustment means for adjusting the position of said energy source relative to said mount flange means; and
- locking means for fixing said source flange means and said mount flange means permanently relative to one another after said focal spot has been positioned at the intersection of said three beam paths.
18. The apparatus as recited in claim 17, wherein said adjustment means includes means for moving said source flange means relative to said mount flange means so as to move said focal spot of said energy source in at least one direction.
19. The apparatus as recited in claim 17, wherein said adjustment means includes means for automatically moving said energy source relative to said source flange.
20. The apparatus as recited in claim 17, wherein said adjustment means includes means for moving said source flange means relative to said mount flange means so as to move said focal spot of said energy source in at least two mutually orthogonal directions.
21. The apparatus as recited in claim 20, wherein said adjustment means includes means for moving said energy source in a third direction normal to said two mutually orthogonal directions.
22. The apparatus as recited in claim 21, wherein said adjustment means includes means for moving said energy source relative to said source flange.
23. The apparatus as recited in claim 16, wherein the energy system is an X-ray imaging system, said system component includes X-ray detection means, and said energy source is an X-ray tube.
24. The apparatus as recited in claim 23, wherein the energy system is a CT scanner system, said system component includes an array of X-ray detectors, and said desired position of said energy source is the position of the focal spot for performing a CT scan.
25. A method of correctly positioning the focal spot of an X-ray source in a CT scanning system of the type including beam defining aperture means and detector means for receiving X-rays from said source passing through said aperture means, said method comprising the steps of:
- precalibrating the position of the focal spot position of said X-ray source prior to mounting the source in the scanning system; and
- positioning the X-ray source in said scanning system without the need to calibrate the position of the focal spot relative to the aperture means and detector means of the CT scanning system.
26. An apparatus for precalibrating the position of the focal spot of an energy source adapted for use in an energy system prior to mounting the energy source in the energy system so that said focal spot will be correctly positioned within the system when the energy source is mounted in the system, said apparatus comprising:
- detector means for receiving and detecting energy emitted by said energy source;
- means for defining at least three beam paths which intersect at a predetermined point in space which is the desired spatial position of said focal spot when said energy source is mounted in said energy system;
- support means for supporting said energy source; and
- adjustment means, coupled to said support means, for controllably adjusting the position of said energy source relative to said support means prior to mounting the energy source in the energy system until the detection of energy by said detector means satisfies an alignment condition,
- wherein the energy system comprises (a) system mount means for supporting said support means in a precise position, and (b) at least one other system component positioned so as to be precisely spaced from the desired position of said energy source and said system mount means, said apparatus further comprising:
- apparatus mount means for supporting said support means and substantially identical to said system mount means to the extent that when the position of said energy source relative to said support means is at the desired position where the detection of energy by said detector means satisfies the alignment condition, the energy source and said support means can be supported by said system mount means and be correctly positioned in said energy system relative to said system component,
- wherein the support means comprises:
- source flange means for securing said energy source to said support means;
- mount flange means for securing said support means to either one of said apparatus mount means and system mount means; and
- adjustment means for adjusting the position of said energy source relative to said mount flange means,
- wherein said adjustment means includes means for moving said source flange means relative to said mount flange means so as to move said focal spot of said energy source in at least two mutually orthogonal directions and in a third direction normal to said two mutually orthogonal directions.
27. The apparatus as recited in claim 26 wherein said adjustment means includes means for moving said energy source relative to said source flange.
28. The apparatus as recited in claim 26, wherein said means for defining at least three beam paths comprises a system of apertures associated with said energy source.
29. An X-ray imaging system of the type including X-ray detector means for sensing predetermined radiation, means for supporting an X-ray source relative to said detector means, and aperture means for defining with said X-ray source an X-ray beam directed at said detector means, said system further comprising:
- an apparatus for precalibrating the position of the focal spot of said X-ray source prior to mounting the X-ray source in the X-ray imaging system so that said focal spot will be correctly positioned within the system when the X-ray source is mounted in the system, said apparatus comprising:
- adjustment means, coupled to said support means, for controllably adjusting the position of said X-ray source relative to said support means prior to mounting the X-ray source in X-ray imaging system until the detection of energy by said detector means satisfies an alignment condition.
30. An apparatus for precalibrating the position of the focal spot of an energy source adapted for use in an energy system prior to mounting the energy source in the energy system so that said focal spot will be correctly positioned within the system when the energy source is mounted in the system, said apparatus comprising:
- detector means to receiving and detecting energy emitted by said energy source;
- means for defining at least three beam paths which intersect at a predetermined point in space which is the desired spatial position of said focal spot when said energy source is mounted in said energy system;
- support means for supporting said energy source; and
- adjustment means, coupled to said support means, for controllably adjusting the position of said energy source relative to said support means prior to mounting the energy source in the energy system until the detection of energy by said detector means satisfies an alignment condition,
- wherein said apparatus further includes means for testing the operational parameters of said energy source, wherein the energy source is an X-ray tube, and the means for testing the operational parameters of said energy source includes means for measuring the X-ray intensity noise from said tube.
31. The apparatus as recited in claim 30, wherein said means for defining at least three beam paths comprises a system of apertures associated with said energy source.
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Type: Grant
Filed: Feb 18, 1997
Date of Patent: Apr 28, 1998
Assignee: Analogic Corporation (Peabody, MA)
Inventors: John Dobbs (Hamilton, MA), Ruvin Deych (Brookline, MA), David Banks (Framingham, MA)
Primary Examiner: David P. Porta
Assistant Examiner: David Vernon Bruce
Law Firm: Lappin & Kusmer LLP
Application Number: 8/800,587
International Classification: G01D 1800; A61B 608;
